Transistors, such as metal oxide semiconductor field-effect transistors (MOSFETs), are the core building block of the vast majority of semiconductor devices. Some semiconductor devices, such as high performance processor devices, can include millions of transistors. For such devices, decreasing transistors size, and thus increasing transistor density, has traditionally been a high priority in the semiconductor manufacturing industry.
A FinFET is a type of transistor that can be fabricated using very small scale processes. FIG. 1 is a simplified perspective view of a FinFET 100, which is formed on a semiconductor wafer substrate 102. A FinFET is named for its use of one or more conductive fins 104. As shown in FIG. 1, each fin 104 extends between a source region 106 and a drain region 108 of FinFET 100. FinFET 100 includes a gate structure 110 that is formed across fins 104. The surface area of the fins 104 in contact with gate structure 110 determines the effective channel of FinFET 100.
FinFET devices have historically been formed using silicon-on-insulator (SOI) substrates. Using an SOI substrate, the conductive fins are formed from the silicon material, while the insulator layer provides isolation between adjacent FinFET devices. Bulk silicon substrates are less expensive than SOI substrates, and FinFET devices can also be fabricated using bulk silicon if appropriate isolation methodologies are utilized.